Condensing devices which are capable of compacting a roving, i.e. a collection of fibers with limited intrinsic twist, also referred to as slubbing, have made use of cylindrical rollers which are formed along their periphery with a row of perforations and flexible belts which likewise can have a row of perforations. A rotatable roller system of this type is described, for example, in German patent document DE 44 26 249 A1. A system using belts is described in EP 0 635 590 A2.
A "mock" yarn, as that term is used in the textile industry, can be a textile strand which is formed from two untwisted rovings or slubbings to which a common twist is imparted. In this operation, the two rovings are wound around one another and the thus resulting collection of filaments has a twist applied to it. A mock yarn of this type differs from a true yarn in that the two components of the mock yarn do not have their own twists. In a true yarn, each of the components can be significantly twisted or spun prior to joining of the spun threads into the yarn. When the two practically untwisted rovings or slubbings are wound around one another to have a common twist, this twist or spun character is observable in the finished product just as it is in true yarns.
In appearance, a mock yarn is similar to a true yarn although in the true yarn, the two components can be individually discernable in spite of the collective twist imparted whereas in a mock yarn, although the twist is visible, it is impossible to distinguish between the components which are twisted together. In the preparation of the mock yarn, therefore, efforts have been made to develop techniques which prevent too tight a twisting of the two components of the mock yarn together.